Radiolucent skin markers are often used in the medical profession to identify particular areas of interest on a patient for a medical imaging exam. A small marker with a radiolucent or semiopaque imaging body can be adhered to the patient's skin next to or near the area of interest, such as a skin protrusion or lesion or a mass below the skin. An example of a prior art skin marker 100 is shown in FIG. 1A. The marker 100 includes a marker substrate 104 with a central opening 106 and an imaging body 102. In FIG. 1A, the imaging body 102 is shaped as a ring that encircles the central opening 106. The marker 100 may be adhered to a patient's skin such that the area of interest is encircled by the imaging ring 102. Other prior art markers include imaging bodies with other shapes, such as a small “BB” or spherical ball. The patient undergoes the medical imaging exam with the marker 100 in place on the patient's skin. The exam may be a computed tomography (CT) scan, x-ray, magnetic resonance imaging (MRI), or other radiographic imaging exam. A common radiographic exam is a mammography, an x-ray imaging exam of breast tissue.
An example of an image of the prior art marker 100 is shown in FIG. 1B. The radiolucent marker appears as a bright ring on the resulting image, so that the radiologist or other medical caregiver can identify the location of the skin protrusion, lesion, mass, or other area of interest that was marked by the marker. The skin marker thus enables the radiologist to make a more accurate diagnosis.
“Radiolucent” and “radiopaque” refer to the radiographic density of the imaging marker. A radiolucent marker allows some radiation to pass through it, while a radiopaque marker reflects radiation and prevents it from passing through the marker. The resulting radiographic image of a radiopaque marker will be denser and will appear brighter than that of a radiolucent marker. Materials with high thicknesses and/or high densities are more radiopaque, and produce a brighter, denser radiographic image, than thinner and/or less dense materials. Thus, the radiographic density of a marker refers to the density of the radiographic image of the marker.
Radiolucent skin markers can fail to register on the radiographic image, especially when the x-ray or other exam is used to image very dense tissue, such as dense breast tissue. Dense tissue requires longer exposure to the radiation in order to obtain a clear image of the tissue. During longer exposure times, the radiation fully penetrates the radiolucent marker, causing it to disappear from the resulting image. Therefore, it is desirable to provide a skin marker that appears more clearly on images of dense tissue.
Radiolucent skin markers can also fail to provide a three-dimensional perspective on the resulting image. A small “BB” or spherical marker appears the same from all directions, so the circle that appears on the x-ray or other image cannot indicate to the radiologist the three-dimensional positioning of the patient. A relatively flat marker with no change in thickness can also fail to add depth to an image. Therefore, it is also desirable to provide a skin marker that adds a three-dimensional perspective to the image.